In the field of optical communication, there is a pressing need to improve the capacity of optical networks. Increasing the capacity of the optical networks may be achieved by buffering the arriving information, arranging it in dense packets and adding headers to the packets to specify their destinations. The buffering and the arrangement of the packets with their headers are done in the electronic domain but, the packets are sent along the optical communication networks in an optical form using Electrical-Optical (E-O) converters. In the current optical communication networks, the optical packets are switched by electronic switches after converting the optical pulses of the packets into electronic signals. When the switching process is completed, by the electronic switches, the packets are resent into their new destination in an optical form using E-O converters. This process incorporates an Optical-Electrical-Optical signal conversion (O-E-O). Both the use of E-O and O-E-O converters is expensive. Additional disadvantages of the use of electronic switches is the buffering process and the information processing which make the electronic switches, together with their time response, relatively slow and creating bottlenecks in the networks.
Accordingly, performing the switching and routing of the packets in the optical domain, by all-optical routers, is very attractive since it can save the use of very expensive E-O converters. However, the fastest optical switches, commercially available today, such as those manufactured by Lynx Photonic Networks 26775 Malibu Hills Road Calabasas Hills, Calif. 91301, have a turn on time of about 5 ns and a latency time of 30 ns. This means that the fastest optical switch, commercially available today, is even slower than the electronic switches used today in the network.
U.S. Pat. No. 5,060,305 entitled “Self Clocked, Self Routed Photonic Switch” filed Oct. 22, 1991 disclosed a system for all-optical packet routing. According to U.S. Pat. No. 5,060,305 (Patent 305) the header is read optically to produce an optical activating signal for activating an optical switch for switching the payload of the packet into one of the two output ports of the switch.
As mentioned above, the use of optical switches has a major drawback of slow switching that creates an unacceptable delay between the headers and the payloads of the packets, resulting in unacceptable bottlenecks in the network. Thus, the disclosure of Patent 305 does not suggest a solution for the relatively slow switching time of the optical switches. A justification to use an all-optical packet routing system exists only in the case where the routing time of such a system is faster than the electronic switches used today. Such a justification is not provided by Patent 305 since its disclosure describes the use of conventional optical switch which is limited, by definition, in its time response since the principal of operation of this switch is base on a material state-change for changing the optical properties of the material from which the switch is made of.
However when the requirement for the combination of fast routing and low cost (by the elimination of the E-O converters) is fulfilled, the all-optical packet routing system is very attractive and practical for being used in all-optical communication networks. Thus, the present invention disclosed the use of ultra-fast all-optical AND and coincidence gates for the purpose of packet gating and routing. The gates according to the present invention are very fast due to their inherent property of being stateless. Stateless means that the gates operates without changing the optical properties of the materials that they are made of and thus there is no limitation on their operation speed due to the lifetime of the charge carriers in the materials associated with the process of changing the state of the material (changing the optical properties). The stateless property of the gates, according to the present invention, make them much faster than the optical switches described in the disclosure of Patent 305 since those switches and others optical switches are always involved, by principle, with the slow process of material state-change.
Accordingly, it is an object of the present invention to provide all-optical packet routing gates and demultiplexing systems that are capable of ultra-fast packet gating and demultiplexing;
Another object of the present invention is to provide ultra-fast all-optical packet routing gates and demultiplexing systems using ultra fast gates;
Another object of the present invention is to provide ultra-fast all-optical packet routing gates and demultiplexing systems using ultra fast gates in the form of all-optical AND and coincidence gates, and
Still another object of the present invention is to provide ultra-fast all-optical packet routing gates and demultiplexing systems using ultra fast gates in the form of all-optical AND and coincidence gates which are stateless devices.